The truth, however, is that Bach synthesized old ideas more than he created new ones. And Tempesta di Mare's season-long cycle of the Brandenburg Concertos revealed how these works hardly appeared out of nowhere, and have antecedents in places you'd think to look (though not all that hard). Telemann, Fasch and Muffat breathed much the same air as Bach (much of it coming from Vivaldi) but with music that can seem so limp, how can you concentrate on it long enough to determine its importance?

Not so with Fasch's Concerto in G and especially Telemann's Concerto in F, both excellent, engaging works heard at Tempesta's Saturday concert at St. Mark's Church. Expanded to 21 members, the group discovered seldom-heard concertos with no central soloist. Many seem like orchestral works with lots of incidental solos that don't come and go so quietly.

The jumping-off point was Brandenburg Concerto No. 1, whose final movement uses the well-worn ritornello technique with stately, recurring orchestral passages punctuated by different instruments giving lofty philosophical discourses. Fasch had less substantial things to say using a similar format, but often teased the ear by allowing it to predict what notes were coming but with constant surprise as to what instrument was playing them.

Telemann's concerto was an unusually ambitious six-movement suite. It had its share of mini-spotlights but also seemed to be made of movements borrowed from different concertos, the bassoon dominating one section, viola da gamba another - always with a piquant orchestration that had the sound picture constantly morphing.

Performances were imposing and forthright, eschewing the polite tidiness of many baroque groups. Tempesta maintained a bit of unruliness that was more than an attractive counterweight to the music's innate formality. Musicologists find implications of changing social order in music of this period; performances that strain at the seams felt appropriate. But the Bach performance was unruly to a fault with particularly fallible baroque-period natural horns. The horns came through later on, however, with the magnetic tension that comes from doing so much with a seemingly primitive set of circular pipes.